1. Field of the Invention
The invention relates generally to a system for rapidly and accurately analyzing a valve. More specifically a test stand and evaluation method is disclosed that analyzes delay valves for use in automotive applications, and moreover accomplishes the analysis at a rate sufficiently fast to make it practical on a high speed automotive production line. This procedure provides a consistent reference pressure which may be set at any desired or predetermined value.
2. Description of the Prior Art
Valves in general, and delay valves for the automotive industry in particular, frequently require calibration or measurement against a standard prior to use. This calibration procedure may utilize atmospheric pressure as a reference pressure. Atmospheric pressure is broadly a function of the altitude above sea level as well as climatic conditions which must be taken into account in any evaluation comparing calibration results. To accommodate this variation in pressure and to make the test results comparable to test results from other locales, a barometric correction formula is utilized. However, prior arrangements for testing with the attendant time for the compensation calculations to be completed are too slow for modern automotive manufacturing situations.
The use of a test stand with a test valve interposed between a pressure regulating valve and an exhaust valve is taught in U.S. Pat. No. 4,050,298 (Hope et al.). An apparatus for testing vehicle pneumatic braking systems is disclosed where a manual valve and a pressure gauge control the supply and exhaust of air to and from the vehicle braking system, and the accompanying variations in pressure in the pneumatic system are noted. There is no teaching of utilizing a reference pressure source nor a known fluid volume. Essentially this reference teaches a procedure to test a pressure tolerance or response to a pressure, not a rate of change at specific operating characteristics or parameters. This system utilizes two manually operable valves to test an operating (braking) system.
Other test apparatus interpose a test sample between a fixed condition or an operating simulation and a force or drive system. In U.S. Pat. No. 4,056,974 a test apparatus for materials or structural components is taught, which apparatus includes a pressure (hydraulic) operated load mechanism controlled by a servo-hydraulic control unit. Impliedly this is a mechanical fatigue test apparatus for the application of both static and dynamic loads to a test piece.
U.S. Pat. No. 4,050,299 illustrates a test stand for a brake testing method for a brake sensor. The test mechanism includes a driver roll and an idler roll having speed sensors associated therewith. The test technique induces a brake lock-up on the driver wheels to actuate the anti-skid system as well as simultaneously generating signals in response to the actuation of the anti-skid system by either sensor.
The above-cited prior art does not teach or disclose a system to analyze a delay valve. Further, none of the teachings illustrates the measurement of a flow-rate, that is the change of pressure with respect to time, through a valve interposed between a fluid of fixed volume and a fluid volume at a known or predetermined pressure. Such empirical flow measurement avoids the determination of flow rate with compensating factors in a mathematical equation. The use of a mathematical adjustment has historically delayed the determination of the flow rate and has demonstrated that such mathematical determinations can not wholly compensate for constantly changing climatic conditions.